<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // console.log('2' - '1');//1
        // console.log('2' - 1);//1
        // console.log('2' * 1);//2
        // console.log('2' / 3);//0.666666.....7
        // 猜测一下取余结果的符号和除数，被除数哪个有关？
        // console.log('2' % 3); // 2
        // console.log('2' + '1'); // 21
        // console.log('1' + 3); // 13

        // console.log('2' - '嘿嘿'); // NaN

        // console.log('1' - '2abc'); // NaN
        // console.log('嘿嘿' + '1a');// 嘿嘿1a
        // console.log('嘿嘿' + NaN);// 嘿嘿NaN
        // console.log('嘿嘿' + 5 * '6');// 嘿嘿30
        // console.log(('嘿嘿' + 5) * '6'); // '嘿嘿5' * '6'      NaN

        // console.log(true + true);//2
        // console.log(true + 5);// 6
        // console.log(true + '8');//true8
        // console.log(true - '8');// -7
        // console.log(false - 3);// -3
        // console.log(false - 3 * '哈哈');//NaN

        // console.log(undefined + undefined);// Number(undefined)  ==> NaN
        // console.log(undefined + 1);// NaN
        // console.log(undefined + '5' + '哈哈');//undefined5哈哈

        console.log(null + true); // 1
        console.log(null + 5);//5
        console.log('null' + (null - 3) + undefined);
        //null-3undefined


    </script>
</body>

</html>